The invention relates to a robotic apparatus for picking of cells, in particular animal cells, or for other biological or chemical applications, such as gel coring or well plate liquid handling, with integrated spectroscopic capability for fluorescence studies, colorimetry and the like.
It is common practice to use fluorescent markers to identify biological or chemical material. Traditionally, these fluorescent markers are investigated using a stand-alone imaging device, referred to as an imager. Two types of imager are now briefly described.
FIG. 6 is a schematic side view of an imager in which a charged coupled device (CCD) detector unit 200 comprising a CCD chip 202 and objective 204 is arranged above a shelf 206 on which a sample dish 208 can be placed centrally about the optical axis “O” of the CCD detector unit 200. Alongside the CCD detector unit 200, banks of blue light emitting diodes (LEDs) 210 are arranged facing the center of the shelf where sample dishes are to be placed. The blue LED banks 210 are used to excite fluorescence in the sample which is then measured by the CCD chip. The imager is built into a light-tight housing 212 accessed by a hinged door (not shown). An imager of this kind is the Fuji LAS-1000.
FIG. 7 is a schematic side view of a scanning imager in which a photomultiplier tube (PMT) 220 and objective 222 are used to measure fluorescence from a sample contained in a sample dish 224 which is excited by raster scanning a 488 nm laser beam 226 generated by an argon ion laser 228 over the sample dish. Raster scanning is achieved by a movable mirror arrangement 230. The scanner is arranged in a light tight housing 232.
In some circumstances it would be desirable to integrate an imaging capability into a robot used for handling well plates or other biological sample containers such as Q-trays, omni-trays, Petri dishes and so forth. This would avoid having to move samples between the robot and the imager. To satisfy this need, a gel picking robot with an integrated imager is known as now described.
FIG. 8 shows a robot for imaging and excision of fluorescent gels according to EP-A-1391719 [1]. A detector unit 240 is mounted in the roof 236 of the robot to image down onto a gel dish placed on a light table. The detector unit 240 contains a CCD chip 242 with associated collection optics 244 and bandpass filter 246. In the middle of the figure, the light table plate 12 is illustrated which lies in the plane of the robot's main bed 5. The light source unit 250 is mounted below the main bed of the apparatus and is based on banks of LEDs 252 whose light is filtered with a filter 253 and homogenised with a diffuser 254. Fluorescence is excited by illuminating the light table from below with the LEDs 252. It is therefore possible to perform fluorescence analysis and gel coring (excision) using the same machine.
Although this design based on transmission-mode optics has been successful, and importantly allows the conventional layout of a microarraying or picking robot to be maintained, the mounting of the detection optics (i.e. the CCD camera) in the roof of the robot with the collection light path extending between the bed of the robot and the roof of the robot is sometimes inconvenient. In particular the robot head and its positioning motors and associated gantries need to be moved out of the way when making fluorescence measurements to avoid blocking the collection light path.